1. Field of the Invention
This invention relates to a thermal transfer recording apparatus and facsimile apparatus, in which ink of an ink sheet is transferred onto a recording medium for recording image thereon.
2. Related Background Art
A thermal transfer printer usually uses an ink sheet with a thermally fusible (or thermally sublimable) ink coated on a base film. The ink sheet is selectively heated according to an image signal by a thermal head to transfer fused (or sublimed) ink onto a recording sheet to record an image. Usually, with this ink sheet ink is perfectly transferred onto a recording sheet by a single image recording operation (so-called one time sheet). Therefore, it is necessary to convey the ink sheet to an extent corresponding to the recording length after completion of recording of one character or one line, and it is required to surely bring a non-used portion of the ink sheet to next recording position. Accordingly, greater amount of ink sheet is used and as compared with a usual heat-sensitive printer for recording on a heat-sensitive sheet, a higher running cost is required for the thermal transfer printer.
To solve the above problems, a thermal transfer printer, in which a recording sheet and an ink sheet are conveyed at different speeds, is proposed as disclosed in U.S. Pat. No. 4,456,392, Japanese Patent Publication No. 58-201686 and Japanese Patent Publication (examined) No. 62-58917. As disclosed in these literature, an ink sheet capable of a plurality of (i.e., n) times of image recording (so-called multiple print sheet) is known in the art. By using this ink sheet, when a recording length L is continuously recorded, the ink sheet which is conveyed after or during each image recording may be conveyed by a smaller length than the length L (L/n: n&gt;1). Thus, the efficiency of use of ink sheet is increased n times as compared with the prior art, and thus it is expected to reduce the running cost of the thermal transfer printer. This recording system is hereinafter referred to as multi-printing.
In the multi-printing using the above ink sheet, ink of the ink layer of the ink sheet is heated by n times. In each heating, a shearing force is generated between fused (or sublimed or like) and non-fused (or non-sublimed or like) ink of the ink layer to effect transfer of ink onto a recording sheet or paper. For this reason, when time from the recording of one line to the recording of the next line is increased to reduce ink temperature, the shearing force between fused (or sublimed) ink and non-fused (or non-sublimed) ink is increased, thus the ink sheet may be difficult to separate from the recording sheet. This is particularly pronounced when recording data of one line contains many black data. Further, this causes remarkable problems in a facsimile apparatus or the like, in which the time interval between one line and the next line is not fixed and tends to be comparatively long.